Different data on different files?

I am developing a game that has many things to be saved. Should I save every thing
onto one file(I dont know how to make it read specific lines) or make different files for everything(Easy, but concerned about junking up mem)?

Well, its up to to you. For example you could make sure the data is always in a specific sequence, so that line 1 contains the level, line 2 contains the weapon and so on.

A more flexible arrangement is to use a keyword followed by its value
For example the file might look like this:level 1
weapon peashooter
Or use a particular delimiter, such as an equal sign:level=2
weapon=rifle

As you can see, there are many choices of how to store the data. Depending on that decision, the means of retrieving the value would vary.

There are two problems here. The first is identifying what type of information is on a particular line. The second is that some data could be either a string or a number (I assume - but you haven't actually said so).

In simple terms, read the first value on the line as a string. Depending on its contents, decide what to do next.

Depends. It could be using a sledgehammer to crack a walnut. It also means the program isn't stand-alone, as it requires the database program to be running too.
You'd still have to design the required table(s) and generate (by hand coding or otherwise) the relevant SQL.

In the right context, MySQL is a good solution. But perhaps for simple cases it's easier to just use an ordinary file.